1. Field of the Invention
The present invention relates to radio frequency (RF) repeaters. More particularly, the present invention relates to adaptive echo cancellation system and method for an on-frequency RF repeater.
2. Description of the Prior Art and Related Information
In a wireless communication system, a mobile unit such as a cellular phone transmits and receives RF signals to and from cell site base stations. An on-frequency RF repeater receives, filters, and re-transmits the signal of interest at the same frequency and at a higher power level. If the product of the forward gain of the repeater and the coupling between antennas is too high, the repeater will oscillate. In general, this is undesirable. An internal feedback path may be used to compensate for the external coupling between antennas, allowing the forward gain of the repeater to be increased if required. This compensation is referred to as “echo cancellation.”
Some residual echo after cancellation is acceptable. However, it is desirable to minimize such residual echo. This may be difficult in some applications, especially for large repeater gains, or for other repeater implementations having difficult cancellation conditions. Accordingly, a need exists for an improved system and method for echo cancellation.